The long-term objective of this study are to find therapeutic approaches to manage the opportunistic infection of Candida albicans. The insensitivity of C. albicans to some of the known antifungal agents and to many known antimetabolites raise questions concerning the mechanism that make this organism insensitive. An understanding of these mechanisms may suggests ways of bypassing or neutralizing these barriers in control of the infection process and should open new opportunities for development of new and specific antifungal agents. Recently, a gene conferring resistance to a number of structurally unrelated agents was isolated from C. albicans by expression of their resistance in S. cerevisiae. This gene is currently referred to as CaMDR, C. albicans multiple drug resistance, and it displays a number of characteristics that have been described for specific transporter such as the ABC transporters. The major objective of the study will be to characterize this mechanism of resistance and to determine whether this gene is a new type of transporter. The experiments are designed to determine the spectrum of this multi-drug resistance and to characterize the gene product by expression the protein in a form that will allow its purification and localization at the cellular level. The importance of CaMDR for survival of C. albicans will be determined by gene disruption and overexpression. Characterization of the gene as a transporter will be performed by functional complementation of known transporters of S. cerevisiae, by subcellular tagging of the proteins and by its ability to insert in lipid bilayer system. Site directed mutagenesis will be performed in specific domains that are found in this gene and are known in other transporter. In search for ways of bypassing the resistance or neutralizing this function tests will be conducted with mutants of S. cerevisiae transformed with CaMDR in which enzymes that appear to mediate the expression of multiple drug resistance in mammalian are affected.